The present invention relates generally to temperature control of workpiece supports for semiconductor processing equipment, and more particularly to rapid heating and cooling of such chucks for resist stripping chambers.
In many semiconductor processing steps, such as etching, deposition, annealing, etc., a workpiece (e.g., a silicon wafer, glass substrate, etc.) is supported within a processing chamber. Gaseous and/or plasma reactants are supplied to the surface of the workpiece while the workpiece is heated to specific temperatures.
Typically, higher temperatures aid in achieving higher reaction rates, and therefore higher workpiece throughput. On the other hand, high temperatures can sometimes cause damage to structures on partially fabricated integrated circuits. Additionally, certain chemical reactions are most efficiently performed at lower temperatures.
Many structures and methods are known in the art for controlling workpiece temperature within the chamber. For example, radiant heat may be supplied to the workpiece through transparent xe2x80x9ccold wallsxe2x80x9d formed of quartz. Radiant heat is particularly used for very high temperature processing (e.g., at greater than 500xc2x0 C.), where it is desirable to raise and lower temperature during the process cycle for each workpiece.
In other arrangements, the temperature of the workpiece support, particularly gravitational, electrostatic or vacuum wafer chucks, can be regulated by resistive heating. Conventionally, xe2x80x9cchucksxe2x80x9d refer to supports for processing workpieces that are kept at constant temperature as workpieces transferred in, processed and transferred out in cycles. Some systems, particularly plasma processing systems, require cooling rather than heating in order to maintain the desired chuck temperature constant.
Regardless of the particular method used to heat the workpiece, workpieces must often be cooled down after processing is completed. For example, a processed workpiece is advantageously allowed to cool to less than about 70xc2x0 C. prior to placement in a low cost storage cassette that would otherwise melt. Since processing time within the chamber is at a premium, such cooling is most typically performed outside of the chamber on a separate station, such that another workpiece can be introduced to the process chamber while the first workpiece is cooling. Workpiece temperature ramping is thereby minimized, as the massive chuck is maintained at a substantially constant temperature while multiple workpieces are sequentially processed.
While a number of heating and cooling systems are known in the art, many of these systems are generally overly complex, too slow, susceptible to particulate generation within the chamber, etc. Accordingly, a need exists for an improved method and apparatus for controlling the temperature of workpiece supports.
In satisfaction of this need, a chuck for supporting a workpiece within a semiconductor processing chamber. The chuck is provided with temperature control mechanisms that permit rapid heating or cooling of the chuck during processing.
In accordance with one aspect of the invention, an apparatus is provided for controlling the temperature of workpieces in a semiconductor processing reactor. The apparatus includes a support with fluid channels. A cold fluid source communicates with the fluid channels via a first supply line, and is configured to maintain a cold fluid maintained at a first temperature. A heat source is maintained at a second temperature, which is higher than the first temperature. A mechanism is provided for conductively transferring heat from the heat source to the support.
In accordance with another aspect of the invention, a method is provided for controlling a workpiece chuck temperature in a process chamber. A first heat transfer fluid circulates through the chuck during a cold phase to bring the chuck to a first temperature. The first heat transfer fluid is removed from the chuck during a hot phase. Also in the hot phase, the chuck is heated to a second temperature higher than the first temperature.
In one embodiment, both a high temperature fluid source and a low temperature fluid source are connected to the fluid channels. By switching between circulation of the high temperature fluid and low temperature fluid, the wafer chuck and thus the workpiece on it, can be rapidly heated or cooled between two different temperatures. In another embodiment, a relatively low temperature fluid is supplied to the fluid channels in the wafer chuck during at least a portion of each cycle. When high temperatures are desired, a heater block is in close contact with the chuck. When low temperatures are desired, the heater block is physically moved from contact with the chuck and lower temperature heat transfer fluid flows through the chuck.
Advantageously, the dual temperature chucks of the preferred embodiments can be used in a photoresist-stripping reactor. In one process, cool fluid is utilized to rapidly reduce workpiece temperature before removing the workpiece from the chuck. In another embodiment, low temperature fluid is kept at a temperature appropriate for a cleaning process, while a high temperature fluid supply or a heater block is kept at a high temperature suitable for photoresist stripping. Similarly, other multiple-step processes, particularly including photoresist stripping, can be conducted at different temperatures rapidly and efficiently using the same wafer chuck.